1021.] 



Artificial Farmyard Mant're. 



403 



varying quantities, until the last portion was saturated with a 

 solution similar in concentration of nitrogen to that of horse 

 urine (1 per cent, of nitrogen). The different portions were then 

 kept in an incubator for 3 months, at the end of which time it was 

 evident that, contrary to expectation, the straw, without, or 

 merely with low doses of nitrogen, had passed through a marked 

 rotting process. On analysis, however, it was found tljat there, 

 had been a definite accumulation of nitrogen in the lower 

 members of the series, while the higher members had lost in 

 some cases the greater portion of their original nitrogen. 

 The Decomposition of Straw inthe Presence of Varying Quantities 

 of Nitrogen as Urea. 



Number of Experiment. 



Treatment 1 2 3 4 5 G 7 8 9 10 

 At beginning 



Straw nitrogen mgrm. 71 71 71 71 71 71 71 71 71 71 



Urea nitrogen „ — 5 10 24 48 97 243 486 729 973 



Total nitrogen „ 71 76 81 95 119 168 314 557 800 1044 



At end of 3 months 



. Organic nitrogen mgrm. 180 177 174 190 192 171 245 269 181 134 



Ammonia ,, „ _ 5 2 4 4 29 74 68 71 76 



Total „ „ 180 182 176 194 196 200 319 337 252 210 



Gain or loss— „ 109 106 95 99 77 32 5 —220 —548 —134 



Dry Matter, loss per cent. 49 46 45 49 47 53 51 48 19 14 



In seven out of the ten cases the final nitrogen of the fer- 

 mented straw varied only between 180 and 210 mgrm., irrespec- 

 tive of the nitrogen content of the original mixture. It should 

 also be noted that the extent of the rotting, i.e., the loss of 

 dry matter, in experiments 1 — 8 w^as very much greater than 

 in 9 and 10 in which the straw was subjected to the action 

 of solutions closely approaching the concentration of ordinary 

 mine, the high alkalinity of the latter exercising a check on 

 decomposition. 



In the main, the nitrogen retained by super-saturated straw, 

 or such as is accumulated b}^ under-saturated straw, as in 

 Nos. 1 — 6 in the above table, appears to be stored up in an 

 organic or non-ammoniacal form. The maximum retention h.as 

 been found to occur within the first four weeks, after which time 

 breakdown of this organic nitrogen to ammonia and conseq'ient 

 loss by volatilisation seems to keep pace with loss of dry matter. 

 Finally, the material assumes a "stabilised " condition — the loss 

 of nitrogen becomes greatly diminished or may be absent alto- 

 gether for long periods. These three phases — accumulative, 

 dispersive and stable — are shown in Fig. 2, which illus- 

 trates the type and extent of the changes taking place in a 

 mixture of straw and urine during a ]^ei-iod of four months. 



B 2 



